Convergence deflection system for a color picture tube

ABSTRACT

In a color picture tube in which a plurality of beams are made to intersect each other at a location between the beam generating sources and the color screen and are focused on the latter by a main focusing lens positioned to dispose its optical center substantially at the location where the beams intersect so that beams emerge from such lens along divergent paths, first and second spaced plates are disposed at opposite sides of each of the divergent paths to electrostatically deflect the respective beam and cause convergence of all of the beams at a common area on the screen when the first and second plates are at different potentials, a high voltage is generated from a horizontal deflecting pulse provided for causing the beams to scan the screen and such high voltage is applied to an anode electrode of the tube and also to each first plate, and a static convergence deflecting voltage is obtained by dividing the aforementioned high voltage and is applied as the potential difference between the first and second plates by which the respective beam is to be deflected. Further, a dynamic convergence deflecting voltage, comprising both parabolic and sawtooth voltages is generated in response to the horizontal deflecting pulse and is superimposed on the static convergence deflecting voltage with provision being made for separately adjusting both deflecting voltages.

Hosoya et al.

[ 51 Jan. 25, 1972 [54] CONVERGENCE DEFLECTION SYSTEM FOR A COLOR PICTURE TUBE [72] Inventors: Mitsuru Hosoya, Kanagawa-ken; l-liroshi Sahara, Tokyo; Minoru Morio, Tokyo, all of Japan [73] Assignee: Sony Corporation, Tokyo, Japan [22] Filed: June 13, 1969 [2]] Appl. No.: 832,907

[50] Foreign Application Priority bata June 15, 1968 Japan ......43/40979 [52] U.S. Cl ..315/13 [5 l] Int. Cl. ...H0lj 29/50 [58] Field ofSearch ..315/l3C [56] References Cited UNITED STATES PATENTS 2,679,6l4 5/1954 Friend ..3l5/l3C 2,716,718 8/1955 Sonnenfeldt 2,928,981 3/1960 Kolesnik et al... 3,l63,797 12/1964 Singleback..... ..3 15/13 C 3,448,316 6/1969 Yoshida et al. ..3 l5/l3 C Primary ExaminerRodney D. Bennett, Jr.

Assistant Examiner-Malcolm F. Hubler Attorney-Albert C. Johnston, Robert E. lsner, Lewis H Eslinger and Alvin Sinderbrand [57] ABSTRACT In a color picture tube in which a plurality of beams are made to intersect each other at a location between the beam generating sources and the color screen and are focused on the latter by a main focusing lens positioned to dispose its optical center substantially at the location where the beams intersect so that beams emerge from such lens along divergent paths, first and second spaced plates are disposed at opposite sides of each of the divergent paths to electrostatically deflect the respective beam and cause convergence of all of the beams at a common area on the screen when the first and second plates are at different potentials, a high voltage is generated from a horizontal deflecting pulse provided for causing the beams to scan the screen and such high voltage is applied to an anode electrode of the tube and also to each first plate, and a static convergence deflecting voltage is obtained by dividing the aforementioned high voltage and is applied as the potential difference between the first and second plates by which the respective beam is to be deflected. Further, a dynamic convergence deflecting voltage, comprising both parabolic and sawtooth voltages is generated in response to the horizontal deflecting pulse and is superimposed on the static convergence deflecting voltage with provision being made for separately adjusting both deflecting voltages.

16 Claims, 7 Drawing Figures PATENTEDJANZSIQYZ 3.638.064

sum '1 or z INVENTORS MITSURU HOSOYA HIROSHI SAHARA MINORU MORIO gay-W ATTORNEY SHEET 2 OF 2 FIG. 2C

m m N Am v w H R V H A 0 W Q m 5M T Ar d U! A J H z a USR Q 500 J m "mm I p 5%, P w L w FIG 20 FIG .25

I I I I I I l I I l I ll /llllnlllilllllL CONVERGENCE DEFLECTION SYSTEM FOR A COLOR PICTURE TUBE This invention relates generally to color picture tubes of the single-gun, plural-beam type, and particularly to tubes of that type in which the plural beams are passed through the optical center of a common electron lens by which the beams are focused on the color phosphor screen.

In single-gun, plural-beam color picture tubes of the described type, for example, as specifically disclosed in the U.S. Pat. No. 3,448,316, issued June 3, 1969 and having a common assignee herewith, three electron beams are emitted or originated by a beam generating or cathode assembly so that one central beam coincides with the optical axis of the electron focusing lens and the two other beams are converged to cross the central beam substantially at the optical center of the lens and thus emerge from the latter along paths that are divergent from the optical axis. Arranged along opposite sides of each of such divergent paths are first and second convergence-deflecting plates at different electrical potentials to deflect the respective beam for causing all beams to converge at a point on the aperture grill or other beam selecting means associated with the color screen, and from which the beams again diverge to impinge on respective phosphor stripes or dots of the screen. After passing between the convergencedeflecting plates, the beams are acted upon by the magnetic fields resulting from the application of horizontal and vertical sweep signals to the corresponding coils of a deflection yoke, whereby the beams are made to scan the screen in the desired raster. It will be apparent that the accurate convergence of the beams at the aperture grill or other beam-selecting means of the tube is dependent upon the convergence-deflecting voltages applied between the plates.

Accordingly, it is an object of this invention to provide a color picture tube of the described type with an improved circuit arrangement by which the convergence-deflecting voltages are generated.

Another object is to provide a circuit arrangement, as above, which produces a static convergence voltage from a high voltage applied to the tube anode, and wherein variations in the anode voltage are accurately reflected in corresponding charges in the static convergence voltage so as to maintain the proper convergence of the beams.

Another object is to provide a circuit arrangement, as above, which produces a horizontal dynamic convergence voltage superimposed on the static convergence voltage while isolating the source of such dynamic convergence voltage from the static convergence voltage.

Still another object is to provide a circuit arrangement, as above, and in which the static and dynamic convergence voltages can be individually controlled without danger from high voltages.

A further object is to provide a circuit arrangement, as above, with improved means for producing the dynamic convergence voltage.

In accordance with an aspect of this invention, the high voltage applied to an anode electrode of the color picture tube and to one of the convergence deflecting plates associated with each divergent path is generated from a horizontal deflecting pulse provided for causing horizontal scanning of the beams, and the static convergence-deflecting voltage applied between the convergence-deflecting voltage applied between the convergence-deflecting plates associated with each divergent path is obtained by dividing the mentioned high voltage.

Further, in accordance with the invention, the dynamic convergence-deflecting voltage which is superimposed on the static convergence-deflecting voltage is generated in response to the horizontal deflecting pulse.

The above, and other objects, features and advantages of the invention, will be apparent in the following detailed description of illustrative embodiments thereof which is to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic sectional view in a horizontal plane passing through the axis of a single-gun, plural-beam color picture tube and which is shown provided with a convergence deflection system according to one embodiment of this invention;

FIGS. 2A-2E are graphic representations of the wave forms of the static and dynamic convergence deflection voltages produced according to this invention; and

FIG. 3 is a diagrammatic view showing a modification of the convergence deflection system of FIG. 1.

Referring now to the drawings in detail, and initially to FIG. 1 thereof, it will be seen that a single-gun, plural-beam color picture tube of the type to which this invention is applied may comprise a glass envelope (not shown) having a neck and a cone extending from the neck to a color screen S provided with the usual arrays of color phosphors S S and 8,, and with an aperture grill G} or beam-selecting means, such as a socalled shadow mask. Disposed within the neck is a single electron gun A having cathodes K K and K each of which is constituted by a beam-generating source with the respective beam-generating surfaces thereof disposed as shown in a'plane which is substantially perpendicular to the axis of the electron gun. In the embodiment shown, the beam-generating surfaces thereof are arranged in a straight line so that the respective beams B B and B emitted therefrom are directed in a substantially horizontal plane containing the axis of the gun, with the central beam 8 being coincident with such axis. A first grid G is spaced from the beam-generating surfaces of cathodes K K and K and has apertures g g and g formed therein in alignment with the respective cathode beam-generating surfaces. A common grid G is spaced from the first grid G and has apertures g g and g formed therein in alignment with the respective apertures of the first grid G Successively arranged in the axial direction away from the common grid G are open-ended, tubular grids or electrodes G G and G respectively, with cathodes K K and K grids G and G and electrodes G G and 6;, being maintained in the depicted assembled positions thereof, by suitable, nonillustrated support means of an insulating material.

For operation of the electron gun of FIG. I, appropriate voltages are applied to the grids G and G and to the electrodes G G and G Thus, for example, a voltage of 0 to minus 400 v. is applied to the grid 6,, a voltage of O to 500 v. is applied to the grid G a voltage of 13 to 20 kv. is applied to the electrodes 6;, and G and a voltage of O to 400v. is applied to the electrode 6,, with all of these voltages being based upon the cathode voltage as a reference. As a result, the voltage distributions between the respective electrodes and cathodes, and the respective lengths and diameters thereof, may be substantially identical with those of a unipotential single beamtype electron gun which is constituted by a single cathode and first and second, single-apertured grids.

With the applied voltage distribution as described hereinabove, an electron lens field will be established between grid G and the electrode G to form an auxiliary lens L as indicated in dashed line, and an electron lens field will be established around the axis of the electrode 6,, by the electrodes G G and G to form a main lens L, again as indicated in dashed lines.

Further included in the electron gun of FIG. 1 are electron beam convergence deflecting means F which comprise shielding plates P and P disposed in the depicted spaced, relationship at opposite sides of the gun axis, and axially extending, deflector plates 0 and O which are disposed, as shown, in outwardly spaced, opposed relationship to shielding plates P and P, respectively. Although depicted as substantially straight, it is to be understood that the deflector plates Q and 0' may, alternatively, be somewhat curved or outwardly bowed, as is well known in the art.

The shielding plates P and P are equally charged and disposed so that the central electron beam B will pass substantially undeflected between the shielding plates P and P, while the deflector plates 0 and Q have negative charges with respect to the plates P and P so that respective electron beams B and 8,, will be convergently deflected as shown by the respective passages thereof between the plates P and Q and the plates P and Q. More specifically, a voltage V, which is equal to the voltage applied to the electrodes 6;, and G may be applied to both shielding plates P and P, and a voltage V which is some 200 to 300 v. lower than the voltage V is applied to the respective deflector plates Q and Q to result in,

the respective shielding plates P and P being at the same potential, and to result in the application of a deflecting voltage difference or static convergence deflecting voltages V between the respective plates P and Q and P and Q and it is, of course, this convergence-deflecting voltage V which will impart the requisite convergent deflection to the respective electron beams B and B In operation, the respective electron beams B B and B which emanate from the beam-generating surfaces of the cathodes K K and K will pass through the respective grid apertures g g and g to be intensity modulated with what may be termed the red", green and blue" intensity modulation signals applied between the said cathodes and the first grid 6,. The respective electron beams will then pass through the common auxiliary lens L to cross each other substantially at the optical center of the main lens L and to emerge from the latter with beams B and B diverging from beam B Thereafter, the central electron beam B will pass substantially undeflected between shielding plates P and P since the latter are at the same potential. Passage of the electron beam 8,, between the plates P and Q and of the electron beam B between the plates P and Q will, however, result in the convergent deflections thereof as a result of the convergence-deflecting voltage applied therebetween, and the system of FIG. I is so arranged that the electron beams B B and B,,, will desirably converge or cross each other at a common spot centered in an aperture of the aperture grill G or other beam selecting means so as to diverge therefrom to strike the respective color phosphors of a corresponding array thereof on screen S. More specifically, it may be noted that the color phosphor screen S is composed of a large plurality of sets or arrays of vertically extending red, green and blue phosphor stripes or dots S S and S with each of the arrays or sets of color phosphors forming a color picture element. Thus, it will be understood that the common spot of beam convergence corresponds to one of the thusly formed color picture elements.

The voltage V applied to the lens electrodes G and G and to plates P and P, is also applied to the screen S as an anode voltage in conventional manner through a nonillustrated graphite layer which is provided on the inner surface of the cone of the tube envelope. Thus, to summarize the operation of the depicted color picture tube of FIG. 1, the respective electron beams B B and B will be converged at aperture grill G and will diverge therefrom in such manner that electron beam B will strike the blue phosphor S electron beam B will strike the green phosphor S and electron beam B will strike the red phosphor 5,, of the array or set corresponding to the aperture at which the beams converge. Electron beam scanning of the face of the color phosphor screen is effected by horizontal and vertical deflection yoke means which receives horizontal and vertical sweep signals whereby a color picture will be provided on the color screen. Since, with this arrangement, the respective electron beams are each passed, for focusing, through the center of the main lens L of the electron gun A, the beam spot formed by impingement of the beams on the color phosphor screen S will be substantially free from the effects of coma and/or aberration of the said main lens, whereby improved color picture resolution will be provided.

The horizontal deflection current-generating circuit indicated generally at 21 is shown to include a horizontal power transistor 22 connected, at its base, to a terminal 22 receiving a horizontal driving pulse from the usual horizontal deflection driving circuit (not shown), a damper diode 23, a flyback transformer 25, the horizontal deflecting coil 26 of the previously mentioned deflection yoke means, and a capacitor 27. The primary winding 25a of transformer 25 is shown connected between a terminal 24 receiving power from a suitable source (not shown) and the collector of transistor 22 having its emitter connected to ground, and the damper diode 23 is connected between primary winding 25a and ground in parallel with transistor 22. The horizontal deflecting coil 26 and the capacitor 27 are connected in series between winding 25a and ground, that is, in parallel with diode 23.

The flyback transformer 25 is shown to have a secondary winding 25b connected to a high voltage-generating means 28 receiving pulses from winding 25b in synchronism with the horizontal driving pulse supplied to terminal 22, and the high voltage-generating means 28 includes a rectifier 28a to produce, from the received pulses, a constant high voltage V p which appears between output terminal 29 and ground. This high voltage V is, as described above, applied to an anode of the picture tube, the electrodes G and G and also the convergence-deflecting plates P and P by way of a terminal 33.

A resistor 30, the secondary winding 31b of an isolating transformer 31 and a variable resistor 32 are connected in series between the output terminal 29 and the ground so that the high voltage V is divided by resistors 30 and 32 into the static convergence voltageV and the voltage V with the voltage V appearing across resistor 30 and being easily adjustable by means of the variable resistor 32. Further, capacitors 44 and 45 are connected in parallel with resistors 30 and 32 for stabilizing the voltages V and V The flyback transformer 25 is further shown to include an additional secondary winding 25c across which an inductance 35 and the resistance of a potentiometer 36 are connected in series to function as an integration circuit 37. Series connected capacitors 38 and 39 are connected between ground and the connection point between capacitor 27 and the horizontal deflection coil 26, that is, capacitors 38 and 39 are 'connected in parallel with capacitor 27, and the connecting point between capacitors 38 and 39 is connected to a middle tap 40 provided on the resistance of potentiometer 36. The connecting point 41 between capacitors 27 and 38 is connected to one end of the primary winding 31a of isolating transfonner 31 through a variable inductor 43, and the other end of winding 31a is connected to the output terminal 42 of potentiometer 36 from which there extends the slider or movable tap 42'. The variable inductor 43 is provided to permit adjustment of the voltage developed at connecting point 41. Finally, a terminal 34 extending from the connecting point between winding 31b of the isolating transformer and variable resistor 32 is connected to plates Q and Q.

The above-described circuits operate as follows:

The pulse voltage developed across winding 25c, and which is synchronized with the horizontal scan period, is converted into a voltage of sawtooth wave configuration by the series connected inductor 35 and the resistance of potentiometer 36, and such voltage of sawtooth wave configuration appears across the resistance of potentiometer 36. Simultaneously, a horizontal deflecting current of sawtooth wave configuration flows through horizontal deflecting coil 26 and the capacitor 27 in series therewith, with the result that a voltage of a parabolic waveform is developed across capacitor 27, that is, between connecting point 41 and ground. This voltage of parabolic waveform is divided by capacitors 38 and 39 so that a voltage of parabolic waveform is developed across capacitor 38, as indicated at 46 on FIG. 2B. The voltage 46 of parabolic waveform is applied to primary winding 31a of isolating transformer 31 through the adjusting inductor 43. The voltage of sawtooth wave configuration appearing across the resistance of potentiometer 36 developes a voltage at the output terminal 42 of the latter in dependence on the position of slider 42' and such voltage at terminal 42 is also applied to primary winding 31a of the isolating transformer. Thus, if slider 42' is at a midposition on the resistance of potentiometer 36, no voltage is developed at terminal 42 as represented by the line 47 on FIG.

2C. However, if slider 42' is displaced in one direction or the other from such midposition, a corresponding voltage of sawtooth configuration is developed at terminal 42, for example, as indicated at 48 or 49 on FIG. 2C, and such sawtooth voltage 48 or 49 is also applied to winding 31a. Therefore, the voltage applied to primary winding 31a of the isolating transformer is a combination of the parabolic voltage 46 and the sawtooth voltage 48 or 49, if any, appearing at terminal 42. Thus, there is produced, across the secondary winding 31b, a horizontal dynamic convergence deflecting voltage e which is either parabolic, as at 51 on FIG. 2D, in the case when there is no voltage developed at terminal 42 as represented at 47 on FIG. 2C, or which is the resultant of parabolic and sawtooth wave forms, as indicated at 52 or 53 on FIG. 2D when the sawtooth voltage 48 or 49, respectively, of FIG. 2C is applied to winding 31a.

Asa result of the'foregoing, the convergence-deflecting voltage V +e as indicated at 54, 55 or 56 on FIG. and which respectively consists of the static convergence voltage V of FIG. 2A superimposed upon the horizontal dynamic convergence voltage e shown at 51, 52 or 53, respectively, of FIG. 2D, is developed across terminals 33 and 34 and, hence, applied between plates P and Q and plates P and Q. It will be apparent that, in the described arrangement according to this invention, the magnitude of the static convergence voltage V is easily controllable by the variable resistor 32 and that the wave shape and magnitude of the horizontal dynamic convergence voltage e are also easily controllable by the potentiometer 36 and the variable inductor 43 which are at the primary winding side of isolating transformer 31. Further, such adjustments for insuring proper convergence of the beams can be effected without coming into contact with any high-voltage portion of the circuits.

It will also be seen that, since the static convergencedeflecting voltage V is produced by dividing the anode voltage V in accordance with the ratio of resistors and 32, which ratio remains constant in the absence of adjustment of resistor 32, the voltage V will be varied in accordance with variations in the anode voltage V Thus, if, for example, the anode voltage V decreases with an increase in the anode current, the voltage V will correspondingly decrease to maintain the ratio V /V at a constant value so as to maintain the proper convergence of the beams.

Referring now to FIG. 3, it will be seen that the circuit arrangement there shown is generally similar to that of FIG. I and has its several components identified by the same reference numerals. However, in the circuit of FIG. 3, the secondary winding 31b of isolating transformer 31 is not connected in series between resistors 30 and 32, but rather has one end connected to the connecting point 57 between those resistors and its other end connected to terminal 34. Thus, the static convergence'deflecting voltage V is produced across resistor 30, that is, between terminal 33 and connecting point 57, and the horizontal dynamic convergence-deflecting voltage e is produced across winding 31b, that is, between connecting point 57 and terminal 34, with the result that the combined convergence-deflecting voltage V +e again appears between terminals 33 and 34. As in the first described embodiment, terminal 33 is connected to the electrodes G and G the anode and the plates P and P of the tube (not shown) while the terminal 34 is connected to the plates 0 and Q of the tube.

Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention.

What is claimed is:

I. In a single-gun, plural-beam cathode-ray tube which includes a beam-receiving screen, beam-generating means for directing a plurality of electron beams toward said screen, and

lens means for focusing said electron beams on said screen and having an optical center through which said beams are all passed with at least two of said beams emerging from said lens means along paths which are divergent to the optical axis of the latter; electron beam convergence-deflecting means to deflect said beams emerging along said divergent paths for convergence of said beams at a common area of said screen. said convergence-deflecting means comprising first and second spaced plates disposed at opposite sides of each of said divergent paths for electrostatically deflecting the respective beam when at different electrical potentials, high voltagegenerating means receiving a horizontal deflecting pulse and operative to generate a high voltage therefrom, means to apply said high voltage as an anode voltage in said tube and also to said first plate associated with each divergent path, voltage-dividing means dividing said high voltage to produce a static convergence deflecting voltage, and means to'apply said" static convergence voltage between said first plate and said second plate associated with each divergent path and thereby establish the potential difference therebetween for deflecting the respective beam.

2. A single-gun, plural-beam cathode-ray tube according to claim 1, in which said voltage-dividing means includes first and second series connected resistors having said high voltage applied thereacross so that said static convergence-deflecting voltage appears across one of said resistors.

3. A single-gun, plural-beam cathode-ray tube according to claim 2, in which one of said resistors is variable to permit adjustment of said static convergence-deflecting voltage obtained by dividing said high voltage.

4. A single-gun, plural-beam cathode-ray ray tube according to claim 2, in which capacitors are respectively connected in parallel with said first and second resistors for stabilizing the voltages appearing thereacross.

5. A single-gun, plural-beam cathode-ray tube according to claim 2, in which there are provided means to generate a dynamic convergence-deflecting voltage, and means to superimpose said dynamic convergence voltage on said static convergence voltage.

6. A single-gun, plural-beam cathode-ray tube according to claim 5, in which said means to superimpose the dynamic convergence voltage on the static convergence voltage is an isolating transformer connected to said means to generate the dynamic convergence-deflecting voltage and to said voltagedividing means.

7. A single-gun, plural-beam cathode-ray tube according to claim 6, in which said isolating transformer has a primary winding connected with said means to generate the dynamic convergence-deflecting voltage and a secondary winding connected in series between said first and second resistors of said voltage dividing means.

8. A single-gun. plural-beam cathode-ray tube according to claim 6, in which said isolating transformer has a primary winding connected with said means to generate the dynamic convergence-deflecting voltage and a secondary winding connected at one end to a connecting point between said first and second resistors of said voltage-dividing means and at the other end to said second plate associated with each of said divergent paths.

9. A single-gun, plural-beam cathode-ray tube according to claim 5, in which the tube has a horizontal deflection coil to cause the beams to horizontally scan the screen when a horizontal deflecting current of sawtooth configuration flows through said coil, and in which said means to generate a dynamic convergence-deflecting voltage includes means to derive from said horizontal deflecting current flowing through said coil a voltage of parabolic waveform, means operating in synchronism with said horizontal deflecting current to produce a voltage of sawtooth waveform and means to combine the voltages of parabolic and sawtooth waveform for constituting said dynamic convergence deflecting voltage.

10. A single-gun, plural-beam cathode-ray tube according to claim 9, in which means are provided to separately adjust the magnitude of said voltage of parabolic waveform and the magnitude and wave shape of said voltage of sawtooth waveform.

11. A single-gun, plural-beam cathode-ray tube according to claim 9, in which a capacitor is connected in series with said horizontal deflection coil to produce a voltage of parabolic waveform across said capacitor, capacitive means divides said voltage across said capacitor to provide said voltage of parabolic waveform to be combined with said voltage of sawtooth waveform, and variable inductor means is connected between said capacitance means and said means to superimpose the dynamic convergence voltage on the static convergence voltage to adjust the magnitude of said voltage of parabolic waveform thus combined.

12. A single-gun, plural-beam cathode-ray tube according to claim 11, in which said means to produce the voltage of sawtooth waveform includes a flyback transformer driven in synchronism with said horizontal deflection current and having a secondary winding, a potentiometer having a resistance and a slider movable therealong, and an inductor connected in series with said potentiometer resistance across said secondary winding to produce a voltage of sawtooth configuration across said resistance, with said voltage of sawtooth waveform to be combined with said voltage of parabolic waveform appearing at said slider of the potentiometer.

13. A single-gun, plural-beam cathode-ray tube according to claim 12, in which said means to superimpose said dynamic and static convergence voltages includes an isolating transformer having a primary winding connected to said slider of the potentiometer and to said variable inductor means.

[4. Horizontal dynamic convergence voltage-generating means for a cathode-ray tube having a horizontal deflection coil to effect horizontal beam scanning in response to the passage therethrough of a horizontal deflecting current of sawtooth configuration, comprising means operating in synchronism with said horizontal deflecting current to produce a voltage of sawtooth waveform, a capacitor connected in series with said horizontal deflection coil to produce a first voltage of parabolic waveform across said capacitor,- capacitive means dividing said first voltage across said capacitor to provide a second voltage of parabolic waveform. means to combine said second voltage of parabolic waveform with said voltage of sawtooth waveform, and variable inductor means connected between said capacitance means and said means to combine said second voltage of parabolic waveform with said voltage of sawtooth waveform to adjust the magnitude of said second voltage of parabolic waveform thus combined.

l5. Horizontal dynamic convergence voltage-generating means according to claim 14, in which said means to produce the voltage of sawtooth waveform includes a flyback transformer driven in synchronism with said horizontal deflection current and having a secondary winding, a potentiometer having a resistance and a slider movable therealong, and an inductor connected in series with said potentiometer resistance across said secondary winding to produce a voltage of sawtooth configuration across said resistance, with said voltage of sawtooth waveform to be combined with said voltage of parabolic waveform appearing at said slider of the potentiometer.

16. Horizontal dynamic convergence voltage-generating means according to claim 15, in combination with means to produce a static convergence-deflecting voltage, and means to superimpose said dynamic convergence-deflecting voltage on said static convergence-deflecting voltage, and means to superimpose said dynamic convergence-deflecting voltage on said static convergence-deflecting voltage including isolating transformer means having a primary winding connected, at its ends, to said variable inductor means and to said slider, respectively. 

1. In a single-gun, plural-beam cathode-ray tube which includes a beam-receiving screen, beam-generating means for directing a plurality of electron beams toward said screen, and lens means for focusing said electron beams on said screen and having an optical center through which said beams are all passed with at least two of said beams emerging from said lens means along paths which are divergent to the optical axis of the latter; electron beam convergence-deflecting means to deflect said beams emerging along said divergent paths for convergence of said beams at a common area of said screen, said convergence-deflecting means comprising first and second spaced plates disposed at opposite sides of each of said divergent paths for electrostatically deflecting the respective beam when at different electrical potentials, high voltage-generating means receiving a horizontal deflecting pulse and operative to generate a high voltage therefrom, means to apply said high voltage as an anode voltage in said tube and also to said first plate associated with each divergent path, voltage-dividing means dividing said high voltage to produce a static convergence deflecting voltage, and means to apply said static convergence voltage between said first plate and said second plate associated with each divergent path and thereby establish the potential difference therebetween for deflecting the respective beam.
 2. A single-gun, plural-beam cathode-ray tube according to claim 1, in which said voltage-dividing means includes first and second series connected resistors having said high voltage applied thereacross so that said static convergence-deflecting voltage appears across one of said resistors.
 3. A single-gun, plural-beam cathode-ray tube according to claim 2, in which one of said resistors is variable to permit adjustment of said static convergence-deflecting voltage obtained by dividing said high voltage.
 4. A single-gun, plural-beam cathode-ray ray tube according to claim 2, in which capacitors are respectively connected in parallel with said first and second resistors for stabilizing the voltages appearing thereacross.
 5. A single-gun, plural-beam cathode-ray tube according to claim 2, in which there are provided means to generate a dynamic convergence-deflecting voltage, and means to superimpose said dynamic convergence voltage on said static convergence voltage.
 6. A single-gun, plural-beam cathode-ray tube according to claim 5, in which said means to superimpose the dynamic convergence voltage on the static convergence voltage is an isolating transformer connected to said means to generate the dynamic convergence-deflecting voltage and to said voltage-dividing means.
 7. A single-gun, plural-beam cathode-ray tube according to claim 6, in which said isolating transformer has a primary winding connected with said means to generate the dynamic convergence-deflecting voltage and a secondary winding connected in series between said first and second resistors of said voltage dividing means.
 8. A single-gun, plural-beam cathode-ray tube according to claim 6, in which said isolating transformer has a primary winding connected with said means to generate the dynamic convergence-deflecting voltage and a secondary winding connected at one end to a connecting point between said first and second resistors of said voltage-dividing means and at the other end to said second plate associated with each of said divergent paths.
 9. A single-gun, plural-beaM cathode-ray tube according to claim 5, in which the tube has a horizontal deflection coil to cause the beams to horizontally scan the screen when a horizontal deflecting current of sawtooth configuration flows through said coil, and in which said means to generate a dynamic convergence-deflecting voltage includes means to derive from said horizontal deflecting current flowing through said coil a voltage of parabolic waveform, means operating in synchronism with said horizontal deflecting current to produce a voltage of sawtooth waveform and means to combine the voltages of parabolic and sawtooth waveform for constituting said dynamic convergence deflecting voltage.
 10. A single-gun, plural-beam cathode-ray tube according to claim 9, in which means are provided to separately adjust the magnitude of said voltage of parabolic waveform and the magnitude and wave shape of said voltage of sawtooth waveform.
 11. A single-gun, plural-beam cathode-ray tube according to claim 9, in which a capacitor is connected in series with said horizontal deflection coil to produce a voltage of parabolic waveform across said capacitor, capacitive means divides said voltage across said capacitor to provide said voltage of parabolic waveform to be combined with said voltage of sawtooth waveform, and variable inductor means is connected between said capacitance means and said means to superimpose the dynamic convergence voltage on the static convergence voltage to adjust the magnitude of said voltage of parabolic waveform thus combined.
 12. A single-gun, plural-beam cathode-ray tube according to claim 11, in which said means to produce the voltage of sawtooth waveform includes a flyback transformer driven in synchronism with said horizontal deflection current and having a secondary winding, a potentiometer having a resistance and a slider movable therealong, and an inductor connected in series with said potentiometer resistance across said secondary winding to produce a voltage of sawtooth configuration across said resistance, with said voltage of sawtooth waveform to be combined with said voltage of parabolic waveform appearing at said slider of the potentiometer.
 13. A single-gun, plural-beam cathode-ray tube according to claim 12, in which said means to superimpose said dynamic and static convergence voltages includes an isolating transformer having a primary winding connected to said slider of the potentiometer and to said variable inductor means.
 14. Horizontal dynamic convergence voltage-generating means for a cathode-ray tube having a horizontal deflection coil to effect horizontal beam scanning in response to the passage therethrough of a horizontal deflecting current of sawtooth configuration, comprising means operating in synchronism with said horizontal deflecting current to produce a voltage of sawtooth waveform, a capacitor connected in series with said horizontal deflection coil to produce a first voltage of parabolic waveform across said capacitor, capacitive means dividing said first voltage across said capacitor to provide a second voltage of parabolic waveform, means to combine said second voltage of parabolic waveform with said voltage of sawtooth waveform, and variable inductor means connected between said capacitance means and said means to combine said second voltage of parabolic waveform with said voltage of sawtooth waveform to adjust the magnitude of said second voltage of parabolic waveform thus combined.
 15. Horizontal dynamic convergence voltage-generating means according to claim 14, in which said means to produce the voltage of sawtooth waveform includes a flyback transformer driven in synchronism with said horizontal deflection current and having a secondary winding, a potentiometer having a resistance and a slider movable therealong, and an inductor connected in series with said potentiometer resistance across said secondary winding to produce a voltage of sawtooth configuration across said resistance, with said voltage of sawtooth waveform to be coMbined with said voltage of parabolic waveform appearing at said slider of the potentiometer.
 16. Horizontal dynamic convergence voltage-generating means according to claim 15, in combination with means to produce a static convergence-deflecting voltage, and means to superimpose said dynamic convergence-deflecting voltage on said static convergence-deflecting voltage including isolating transformer means having a primary winding connected, at its ends, to said variable inductor means and to said slider, respectively. 